1. Field of the Invention
The present invention relates to a balloon catheter for use in combination with a side view endoscope in medical treatment and the like, and a method for fabricating a sheath for use in the balloon catheter.
2. Background Art
Conventionally, a balloon catheter with a balloon attached at the distal end has been used as medical equipment for removing gallstones and the like. When removing gallstones with use of this balloon catheter, cannulation is performed from the duodenal papilla into the bile duct, and in the bile duct, the balloon is inflated to about a size which allows the balloon to be contacted with the bile duct wall. Then, the inflated balloon is used to rake gallstones out of the bile duct.
Accordingly, the abovementioned balloon catheter is required to have properties such as a high cannulation capability (insertability) into the bile duct, and a capability of inflating the balloon to a size which allows close contact with the inner wall of the bile duct.
When gallstones are formed in the bile duct, the bile flow is impaired, which often causes expansion of the diameter of the bile duct itself. Therefore, to deal with such a case, there is an increasing demand for a balloon catheter comprising a balloon which is inflatable to a larger diameter.
The maximum inflation diameter of the balloon is mostly determined by the material of the balloon, the dimension of the inner diameter of the balloon when deflated, and the like. Accordingly, to achieve a greater maximum inflation diameter, it is necessary to increase the dimension of the deflated balloon to greater than that of a conventional balloon catheter, if the same material is used for these balloons.
As a balloon catheter which has realized a greater maximum inflation diameter, there is known a balloon catheter in which the inner diameter of the balloon is increased and the catheter's distal end for fixing the balloon is thickened (for example, refer to Japanese Unexamined Utility Model Application, Publication No. Hei. 5-63551).
In addition, as another example, there is also known a balloon catheter comprising a so-called barrel-shaped or lantern-shaped balloon in which only the central portion is formed thick and the axial ends to be fixed to the catheter are formed thin, so as to increase the maximum inflation diameter of the balloon while retaining thinness of the outer diameter of the catheter's distal end (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2001-46378).